#include <stdio.h>

int main(int argc, char *argv[])
{
    double sum = 0, h = 100;

    int n = 0;
    scanf("%d", &n);

    for (size_t i = 0; i < n; i++)
    {
        sum += h;
        h /= 2;
        if(i!=n-1)
            sum += h;
    }
    printf("%.4f", sum);

    return 0;
}